**Definition:**

The displacive distortion of a given rigid group is not completely described by _atom_site_displace_Fourier_. The rigid rotation of the group around a given axis passing through a fixed point (for example, the centre of mass of the group) is usually parameterized by Fourier series. Each term of the series commonly adopts two different representations: the sine-cosine form, Rc cos(2\p k r)+Rs sin(2\p k r), and the modulus-argument form, |R| cos(2\p k r+\y), where k is the wave vector of the term and r is the atomic average position. _atom_site_rot_Fourier_param_cos is the cosine coefficient (Rc) in degrees corresponding to the Fourier term defined by _atom_site_rot_Fourier_atom_site_label, _atom_site_rot_Fourier_axis and _atom_site_rot_Fourier_wave_vector_seq_id.

Appears in list containing _atom_site_rot_Fourier_param_id

Enumeration default: 0.0

**Type:** numb

**Category:** atom_site_rot_Fourier_param

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